1. Ozone Modeling over the Western U.S. -- Impact of National Controls on Ozone Trends in the Future Rural/Urban Ozone in the Western United States -- March 10, 2004 Pat Dolwick, Carey Jang, Sharon Phillips U.S. EPA – Office of Air Quality Planning and Standards

2. Purpose/Outline Purpose: Present some limited results from EPA ozone modeling simulations estimating future trends in ozone over the western U.S. Outline: Expected ozone trends over western U.S. Modeling ozone in the western U.S. w/ CMAQ Effect of intercontinental transport on ozone

3. Expected Ozone Trends – Federal Emissions Reductions Eastern U.S. EGU NOx controls Modeling studies have shown impacts from eastern U.S. NOx in Big Bend N.P. and Dallas. Total NOx reduction of ~ 28%, beginning 5/03 Tier 2 / Gasoline Sulfur Issued in 2000 SUVs, light trucks, vans subject to same emissions standards as cars (0.07 gpm NOx) 77-95% less NOx emissions from category Effective in model year 2004, phase in (07/09)

4. Contribution to High Ozone in the Dallas Region CAMx source apportionment: Source: IAQR 70 10 3 3 4 2 1 1 1 1 1 1 1

5. Expected Ozone Trends – Federal Emissions Reductions Heavy Duty Engine & Diesel Sulfur Issued in 2001 Emissions standards for heavy-duty trucks and buses, plus fuel sulfur limits 95% less NOx emissions from category Effective in model year 2006/07, phase in (09/10) NonRoad Engine & Diesel Sulfur Proposed in 2003, Expected final in April 2004 Emissions standards for construction, agricultural, and industrial equipment 90% less NOx emissions from category Effective in model year 2008, phase in through 2014

6. Expected Ozone Trends – Future NOx Emissions Changes

7. Expected Ozone Trends – NonRoad Emissions

8. Expected Ozone Trends – NonRoad Modeling Analyses CAMx, v3.10 36/12 km 11 layers, 4.8 km Two July 96 episodes (25 days) 2020 base/control 2030 base control

9. Expected Ozone Trends – NonRoad Modeling Analyses Mean normal. bias = -21% Gross error = 26% Improvement from Tier 2 CARB Emissions BEIS3 Emissions Only 3 subregions met EPA recommended targets, but went forward w/ analysis given use of model in relative mode.

10. Expected Ozone Trends – NonRoad Modeling Analyses Most portions of the western U.S. are projected to have a reduction of 2-10 ppb in peak 8-hr ozone levels by 2020 Greater reductions in majority of CA Disbenefits in LA, SF, DEN (small) & PHX (small)

11. Expected Ozone Trends – NonRoad Modeling Analyses Most portions of the western U.S. are projected to have a reduction of 2-10 ppb in peak 8-hr ozone levels by 2030 Greater reductions in majority of CA Disbenefits in LA, SF, & PHX

12. Expected Ozone Trends – Relative Reduction Factors Use relative change in model ozone (base vs. future) in conjunction with present-day design values to estimate the design value in the future. NR analyses used 1999-2001 ambient data For this presentation, used preliminary 2001-2003 ambient data Only uses predictions >= 70 ppb Compares 9-cell average, multi-day mean, 8-hr max Explained in more detail in EPA 8-Hour modeling guidance

13. 1999-2001 Eight Hour Ozone Design Values

14. Projected 2020 Eight Hour Ozone Design Values

15. Expected Ozone Trends – NR Modeling: Arizona

16. Expected Ozone Trends – NR Modeling: Colorado

17. Expected Ozone Trends – NR Modeling: Nevada

18. Expected Ozone Trends – NR Modeling: New Mexico

19. Expected Ozone Trends – NR Modeling: Oregon

20. Expected Ozone Trends – NR Modeling: Utah

21. Expected Ozone Trends – NR Modeling: Washington

23. Expected Ozone Trends – NonRoad Modeling Analyses 8-hour ozone levels are generally expected to decrease slightly in the Western U.S. over the next 10-25 years Decrease of ~ 5%: Albuquerque, Denver, Phoenix, Salt Lake City, Tucson, & rural areas Larger decreases: Portland, Seattle Model results uncertain (your results may vary) Certain Western U.S. cities are likely to maintain design values near/just below the NAAQS over the next 0-20 years w/o local control – will depend on year-to-year meteorological variability.

24. CMAQ Western U.S. Ozone Modeling EPA has modeled ozone over the western U.S. using several model configurations Proof of Concept (left): 1996 episode, 36/12km, 2001 release of CMAQ Continental U.S.: entire year of 1996, 36km, 2002 release of CMAQ Continental U.S.: entire year of 2001, 36km, 2004 release of CMAQ, in progress

25. CMAQ Western U.S. Ozone Modeling – 1996 Application Model performance evaluation indicated greater negative bias in the western U.S. in the summer than in 36/12 CAMx Mean normalized bias = -11.7% Normalized gross error = 23.2 % East US (annual): bias = -1.2%; error = 18.6% West US (annual): bias = -26.5%; error = 29.9% East US (summer): bias = 0.8%; error = 18.7% West US (summer): bias = -27.0%; error = 30.5%

26. CMAQ Western U.S. Ozone Modeling – 1996 Application RRF-derived estimates of future design values differ across 3 models CMAQ and CAMx are more similar than REMSAD In future, EPA hopes to consolidate ozone and PM modeling into a single, comprehensive modeling platform

27. Default BCs/ICs : EPA Default Profile v6b Ozone = 35 ppb GCMx (GEOS-CHEM + Default) BCs/ICs : 21 key species from “GEOS-CHEM” + the rest from “Default” (Needed for CMAQ runs) Ozone ~ 10-25 ppb (surface) Ozone ~ 200 ppb (top model layer, 400-100 mb) Highlights of differences using GCMx BCs/ICs July 2001 (monthly avg.): Lower O3 (3~10 ppb) over the west coast Moderately higher PM 2.5 (mainly PM sulfate) over U.S. Effect of Intercontinental Transport – Sensitivity Tests

28. (July monthly avg., 2001) O 3 diff. (GEOS/CHEM BCs/ICs – Default BCs/ICs)  O 3  O 3 (%) Source: Jang (2004), personal communication

29. (July 22, 2001) O 3 diff. (GCM BCs/ICs – Default BCs/ICs)  O 3 (daily avg.)  O 3 (8-hr max) Source: Jang (2004), personal communication